Communication networks include registers, such as home location registers (HLRs) and visitor location registers (VLRs), that store data related to subscribers to the particular communication network. This data identifies whether the subscriber subscribes to particular services and whether there are any restrictions on the subscriber. This data also includes the subscriber policy, which governs the overall operational behavior of the subscriber. Typically, the subscriber policy is relatively static. In some systems, a subscriber may be provisioned to operate primarily in a master network, and optionally in one or more slave networks. Because policies are typically static, in these systems the slave networks may cache the policy in their own visitor location register to minimize access overhead to the home location register.
FIG. 1 illustrates a conventional wireless communication system, which includes a first network 110 and a second network 150. The first network 110 includes two or more base transceiver stations 115a and 115b coupled to a mobile switching center (MSC) 120. Subscriber data for mobile stations supported by MSC 120 is stored in home location register (HLR) 130 and/or visitor location register (VLR) 135. Similarly, the second network 150 includes two or more base transceiver stations 155a and 155b coupled to mobile switching center 160. In the second network 150, subscriber data for mobile station supported by mobile switching center 160 is stored in home location register 170 and/or visitor location register 175.
A home location register stores subscriber data for subscribers of that particular network, while a visitor location register stores data for subscribers roaming from other networks. Assume that a mobile station is a subscriber in the first network 110 and is registering in the second network 150. The mobile station's subscriber data is stored in home location register 130. Typically, the mobile station sends a registration request a base transceiver station in the second network 150, which in turn forwards the registration request to mobile switching center 160. Based on the registration request, mobile switching center 160 recognizes that the mobile station is a subscriber in the first network 110, and sends a request for the subscriber data to mobile switching center 120. Mobile switching center 120 retrieves the subscriber data from home location register 130 and forwards the subscriber data to mobile switching center 160. Mobile switching center 160 then stores the subscriber data in visitor location register 175.